The invention relates in general to recording/writing on magnetic storage media and, more particularly, to an improved servo write head for writing servo patterns on magnetic tape.
With ever denser data, recording and reading data on magnetic storage media requires increasingly precise positioning of magnetic read and write heads. Data is often written in parallel tracks. The read/write heads must be moved quickly and positioned over particular data tracks as data is read or recorded. The magnetic heads record and read data as relative movement occurs between the heads and the magnetic storage media in a transducing, usually lengthwise, direction. The heads are generally moved from one track to another track across the width of the tracks in a translating direction. For example, a magnetic tape typically contains data tracks that extend along the length of the tape parallel to the tape edges in the transducing direction. The heads move from track to track in the translating direction across the tape from edge to edge.
Storage devices that read and record data on magnetic media can use servo control systems to properly position the heads in the translating direction. High performance linear tape drives are beginning to implement closed-loop servo systems for track following in order to record at high area densities. The servo control systems derive a position signal from a magnetic servo read head that reads servo position information recorded in servo tracks on the storage media. Servo position information is recorded on magnetic tapes, for example, as part of the pre-formatting process between manufacture of raw blank tape and end user packaged tape cartridges. A magnetic servo write head in a servo writer machine records the servo information on the tape, usually in bulk before the tape is cut and assembled into cartridges. One such servo write head and a corresponding servo position system is described in U.S. Pat. No. 5,689,384 titled Timing Based Servo System For Magnetic Tape Systems.
U.S. patent application Ser. No. 08/959,509 titled Batch Fabricated Servo Write Head describes a servo write head that may be fabricated in batches rather than individually as in prior art servo write heads. Referring to FIGS. 1 and 2, the batch fabricated servo write head 100 of the ""509 application includes a flat tape recording surface 102 on a thin layer 104 of high moment magnetic material and rounded leading and trailing edges 106 and 108. Servo patterning gaps 110 are formed in layer 104 at the center of bearing surface 102. Tape 112 contacts head 100 at the leading and trailing edges 106 and 108. It has been discovered that excessive wear along the leading and trailing edges may occur from the contact with tape 112. Excessive wear can generate debris that can clog the tape/head interface at recording surface 102 or scratch tape 112. Excessive wear can also alter the shape of the head at leading and trailing edges 106 and 108 resulting in an undesirable contour with increased tape/head spacing. Moreover, excessive wear may cause the thin magnetic layer 104 to peel if its edge coincides with the head/tape contact region at leading and trailing edges 106 and 108.
Prior solutions to the problem of excessive head wear generally include the widened head pads described in U.S. Pat. No. 5,055,959 titled Tape Head With Low Spacing Loss Produced By Narrow And Wide Wear Regions, applying wear resistant coatings to the entire head, and the xe2x80x9ccontactxe2x80x9d head described in the ""384 patent. The ""959 patent describes a servo write head that utilizes widened pads to reduce the contact pressure between the tape and the head. Widened head pads, however, are not practical in radiused edge/flat servo write heads such as the batch fabricated heads shown in FIGS. 1 and 2. Although the application of a wear resistant coating to the entire head as shown in FIG. 14 of the ""509 application may be effective in reducing wear, the coating is less desirable because it increases the magnetic spacing between the tape and the head which may reduce the effectiveness of the head recording servo patterns on the tape. The contact head described in the ""384 patent, which presumably just wears down until it no longer functions, is undesirable due to the comparatively short useful life and the potential changes to the recording characteristics as the head wears.
Accordingly, the present invention is directed to a head in which the leading and/or trailing edges are constructed with wear resistant material to reduce wear at the locations where the tape contacts the head while minimizing any adverse effects on the performance of the head that is recording servo data on the tape. In one embodiment of the invention, a localized layer of wear resistant material is formed on the leading edge where the tape contacts the head before passing over the head recording surface. In a second embodiment, the leading edge is formed from wear resistant material embedded in the head structure adjacent to the recording surface. And, in a third embodiment, the leading edge is formed as a wear resistant material strip affixed to the side of the head structure. For each embodiment, the wear resistant material may also be applied in the manner described to the trailing edge where the tape may also contact the head after passing over the recording surface.
The use of wear resistant materials at the leading and trailing edges as summarized above will reduce wear while helping to maintain the desired spacing between the head recording surface and the tape over the full life of the head. The invention should also help reduce or eliminate debris from the head that might otherwise be generated during the servo recording process which, in turn, should help minimize head clogging and tape scratching. For those types of heads that use a thin layer of magnetic material embedded in or applied to the head structure at the recording surface, such as that shown in FIGS. 1 and 2, the invention should help reduce or eliminate the potential for this magnetic layer to delaminate from the base head structure at the leading or trailing edges.